1. Field of the Invention (Technical Field)
The present invention relates to fiber optic switches, particularly the use of electro- or magneto-active materials to cause optical fibers to undulate.
2. Background Art
Note that the following discussion refers to a publication by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publication herein is given for more complete background and is not to be construed as an admission that the publication is prior art for patentability determination purposes.
Present day optical fiber technologies are revolutionizing the telecommunications industry. Tremendous advances have been made in the field of telecommunications over the past decade. It has been estimated that this technology is capable of carrying tens of millions of conversations simultaneously on a single optical fiber. Optical fiber communication systems offer many advantages over systems that use copper wire or radio frequency links as a transmission medium. They include lower transmission losses, higher bandwidths, higher transmission rates, lower implementation costs, greater reliability and greater electrical isolation characteristics. It is clear that optical fiber communication will dominate the telecommunications industry in the very near future because of advantages such as these.
Fiber optic switching is an important component in any telecommunication system. These systems use switches to establish communication channels among two or more of their interfaces. An optical fiber switch is capable of optically connecting, or aligning, any one of a first group of optical fibers with any one of a second group of optical fibers, or vice versa, enabling an optical signal to propagate through the optical interface junction from one fiber to the other.
When two optical fibers are aligned end-to-end, light entering one fiber (the input or sending fiber) will continue into and through the second fiber (the output or receiving fiber) while the two adjacent ends, or faces, are aligned and close together. Fiber optic switches misalign or disjoin the adjacent ends of the fibers by moving one or both of the two ends. By moving, for example, the first fiber's end to a new location, the signal, in this case light, can be redirected into another, third fiber, by aligning the first fiber's end with an end of the third fiber.
Lateral separation of the two adjacent ends will result in loss of light between the two fibers so that a light absorber is provided beside the fiber which either moves into place as the receiving fiber moves away or stays in place as the sending fiber moves away. Space is provided for this motion. This effectively switches the signal off. The discontinuity between the fiber ends may be either perpendicular to the fiber axis or at some angle to the axis but the gap is minimal when the fibers are aligned. Fibers may be collected into a bundle, a fiber optic cable, with a structure set up at the active location to permit the required motion of a fiber end. A fiber bundle can be separated from a circular bundle cross-section to a linear arrangement where the fibers are in a straight line at the switch but reformed into a bundle again at the device exit.
Optical fiber switches generally utilize fiber positioning means, alignment signal emitter means and computer control means. Normally, a fiber positioning means is provided near the end of one fiber to selectively point the end of that fiber in one fiber group toward the end of another fiber in the other fiber group to perform a switched optical transmission. Patents proposing to perform such switching actions in fiber optic telecommunication systems include: U.S. Pat. No. 5,024,497, to Jebens, entitled "Shape Memory Alloy Optical Fiber Switch," which discusses switching activated by a shape memory alloy wire in a transverse direction. U.S. Pat. No. 4,512,036, entitled "Piezoelectric Apparatus for Positioning Optical Fibers," U.S. Pat. No. 4,543,663, entitled "Piezoelectric Apparatus for Positioning Optical Fibers," U.S. Pat. No. 4,651,343, entitled "Piezoelectric Apparatus for Positioning Optical Fibers," and U.S. Pat. No. 5,524,153, entitled "Optical Fiber Switching System and Method Using Same," all to Laor, use piezoelectric bimorphs for positioning optical fiber switches. U.S. Pat. No. 4,303,302, to Ramsey, et al., entitled "Piezoelectric Optical Switch" discusses other forms of piezoelectric bimorphs for optical fiber switching.
Other patents discussing fiber optic switching include: U.S. Pat. No. 5,812,711, to Glass, et al., entitled "Magnetostrictively Tunable Optical Fiber Gratings;" U.S. Pat. No. 5,812,711 to Malcolm, et al., entitled "Magnetostrictive Tunable Optical-Fiber Gratings;" U.S. Pat. No. 4,759,597, to Lamonde, entitled "Mechanical Switch for Optical Fibers;" U.S. Pat. No. 4,415,228, to Stanley, entitled "Optical Fiber Switch Apparatus;" U.S. Pat. No. 5,004,318, to Ohashi, entitled "Small Optical Fiber Switch;" U.S. Pat. No. 4,844,577, to Ninnis, et al, entitled "Bimorph Electro Optic Light Modulator;" U.S. Pat. No. 4,512,627, to Archer, et al., entitled "Optical Fiber Switch, Electromagnetic Actuating Apparatus with Permanent Magnet Latch Control;" U.S. Pat. No. 5,699,463, to Yang, et al., entitled "Mechanical Fiber Optic Switch;" U.S. Pat. No. 5,841,912, to Mueller-Fiedler, entitled "Optical Switching Device;" U.S. Pat. No. 5,647,033, to Laughlin entitled "Apparatus for Switching Optical Signals and Method of Operation;" U.S. Pat. No. 4,886,335, to Yanagawa, et al., entitled "Optical Fiber Switch System;" and U.S. Pat. No. 4,223,987, to Kummer, et al., entitled "Mechanical Optical Fiber Switching Device." These patents disclose various methods for fiber optic switching, including mechanical devices such as rods, motors, and adapters, as well as wave guides and reflectors.
The Ohashi, Ramsey, Ninnis, Stanley, Jebens, Glass, and Laor patents disclose various methods and apparatuses that use piezoelectrics, magneto-strictive materials, and shape memory alloys, for bending the fiber; however, these patents are either complicated in their configurations or require additional mechanical means beyond these materials. The present invention overcomes deficiencies in the prior art by directly adhering an electro- or magneto-active material to the optical fiber, or fiber optic cable, itself, longitudinally to cause the fiber to undulate to the desired "2-1/2-D" position, without additional means of support or other mechanical means. The designation 2-1/2-D signifies that the displacement of the fiber may produce both a lateral and a longitudinal change. The present invention is, therefore, a novel configuration for undulating an optical fiber or fiber optic cable.